It has long been known that hypochlorite bleaches and peroxygen bleaching compounds such as hydrogen peroxide, sodium percarbonate and sodium perborate monohydrate or tetrahydrate, for example, are useful in the bleaching of fabrics, textiles and other similar materials. Preformed peracid chemistry was subsequently developed and found to achieve enhanced bleaching action compared to the peroxygen bleaching compounds noted above.
More recently, peracid precursor or activated bleach chemistry has been developed as a further alternative bleaching composition. Generally, this chemistry involves the use of peracid precursors or activators in an aqueous solution for in situ generation of peracid.
A number of peracid precursors or bleach activator systems have been developed in the prior art. For example, representative systems have been disclosed by U.S. Pat. No. 4,283,301 issued Aug. 11, 1981 to Diehl and U.S. Pat. No. 4,412,934 issued Nov. 1, 1983 to Chung et al. Many other prior art references have also disclosed peracid precursor systems suitable for in situ generation of a peracid within an aqueous solution which may be a wash solution containing fabrics to be cleaned.
Techniques for enhancing bleach performance of preformed peracids have been disclosed by a number of prior art references. In particular, U.S. Pat. No. 4,391,725 issued Jul. 5, 1983 to Bossu disclosed and claimed a granular hydrophobic peroxyacid laundry product in the form of a preformed peracid bleach encased or permeated within a nonwoven fabric pouch. An acid additive, indicated as having a pKa of from about 2 to about 7, was combined with the hydrophobic peracid in the pouch in order to aid in release of the peracid from the pouch, thereby enhancing bleach performance. U.S. Pat. No. 4,473,507 issued Sep. 25, 1984 as a division from the above patent and related to similar subject matter. U.S. Pat. No. 4,391,723 issued Jul. 5, 1983 to Bacon and Bossu as well as U.S. Pat. No. 4,391,724 issued Jul. 5, 1983 to Bacon also related to similar subject matter and appeared to demonstrate advantages in the inclusion of boric acid or other acids together with the preformed peracids for improving bleach performance. British Patent Publication 1,456,592 disclosed the use of both acid and alkaline pH-adjustment agents together with preformed peroxyacid bleach materials for enhancing stain removal capabilities.
To the extent that the prior art references discussed above are of assistance in facilitating an understanding of the present invention, they are incorporated herein as though set forth in their entirety. However, none of the above preformed peracid references either disclosed or suggested bleaching methods or bleaching products including peracid precursors or activators for in situ generation of the peracid in aqueous wash water.
At the same time because of the advantages of peracid precursors as noted above, it has been found desirable to further enhance bleaching performance of such systems in order to make them even more effective and/or efficient.